A river runs near it

Western water developers push for kinder, gentler 'off-channel' reservoirs

Water for the off-channel Black Rock Reservoir would be pumped from the Columbia River into a dammed dry valley. The reservoir would supply Yakima Valley farms and towns, freeing water from existing reservoirs for release back into the Yakima River system to benefit dwindling salmon runs at critical times.

Adapted from the bureau of reclamation

Colorado Highway 287 winds through the dry valley where the proposed off-channel Glade Reservoir would store water diverted from the Cache La Poudre River.

Central Washington's Yakima Valley sits on the dry side of the
Cascades, where just eight inches of precipitation falls each year. But
the arid valley has rich volcanic soils and an accommodating climate of
warm days and cool nights, and after the U.S. Bureau of Reclamation
built six dams in the early 20th century, farms and orchards flourished
here. Thanks to the water brought via pipes and canals, the Yakima
region became known as the nation's "Fruit Bowl." Today, apple, pear
and cherry trees cover 92,000 acres, and wine grapes spread over
another 10,000. The valley also produces three-fourths of the country's
hops, a $100 million crop.

In recent years, though, the region has reaped a different bumper crop.
Since 2000, the city of Yakima has added 12,000 new residents -- a 17
percent jump in population -- and the valley is thirstier than ever.
That's a familiar story in the growing West. But the era of big dam
building has passed, and water developers have turned to a new round of
mid-sized structural solutions to increase water supply.

In 2003, Congress ordered Reclamation to look into building a
10-mile-long reservoir in a dry valley about 20 miles east of Yakima,
where it won't block the Yakima River. The proposed $6.7 billion Black
Rock Reservoir would hold 1.6 million acre-feet of storage behind a
755-foot-high dam, making it one of the largest reservoirs built in the
U.S. in recent decades.

Similar proposals are under review throughout the West. Northern
Colorado is considering an off-channel project that would tap the Cache
la Poudre River. California wants off-channel storage near the
Sacramento River, as part of a $9.3 billion water initiative, and
Wyoming is exploring off-channel sites in the Green River Basin. And in
Utah, water managers want to build a 140-mile-long, $1 billion pipeline
to bring water from Lake Powell to the city of St. George and the
surrounding area. To help sell the projects, water developers have
figured out ways to mitigate some resource damage and help low-flowing
rivers and fish in need of habitat.

But river advocates say Black Rock and other projects billed as
environmentally friendly promise far more than they can deliver. And
the high costs involved may put an end to this new dam era before it
even begins.

The Bureau of Reclamation and other dam builders have already blocked
and diverted most of the West's major rivers, flooding the deep valleys
and canyons best suited for big reservoirs. Black Rock is a comparative
puddle next to the 150-mile-long water hole behind Grand Coulee Dam
(although Black Rock's dam would be taller). And with national
environmental laws making it harder to get monumental projects
approved, the glory days of dam building are history.

As a result, new dam proposals tend to demonstrate an environmental
sensitivity that was seldom seen in last century's water planners.
Off-channel dams and reservoirs, though not a new engineering feat,
have become increasingly common among water proposals in recent years.
They are built in dry canyons or valleys, instead of on the main course
of a river.

In the Yakima Valley, peak flows (above target flows set for salmon)
would be diverted from the Columbia River and pumped over a ridgeline
into Black Rock Valley. The new reservoir would supply growing
municipalities and existing irrigation canals to help drought-plagued
farmers, freeing some of the water stored behind existing dams in the
Yakima River Basin to be released into the river system when it would
most benefit salmon.

The off-channel construction would neither block fish passage on the
Yakima nor inundate biologically rich riparian habitat and floodplains.
According to University of Montana river ecologist Jack Stanford, the
basin offers one of the Northwest's best opportunities for salmon
restoration. The increased flows could support 1 million salmon in
a river system where only about 3,000 now survive.

"Looking at the broad range of benefits, I don't see any environmental
downside to this," says Sid Morrison, a former congressman who now
chairs the Yakima Basin Storage Alliance, a coalition of Black Rock
supporters.

There are no salmon in Colorado's Cache la Poudre River. But Glade
Reservoir's supporters are equally enthused about the project's
environmental and agricultural benefits. Former U.S. Congressman Hank
Brown, R-Colo., who mediated a fight over a main-channel dam on the
Poudre in the 1980s, praises Glade as "an enormous plus for the
environment."

Glade would hold 177,000 acre-feet of water behind a 250-foot-tall dam
in a hogbacked valley off the Poudre River channel. The stored water
would be pumped from the river during spring high flows to meet the
demands of 15 fast-growing rural towns and bedroom communities between
Fort Collins and Denver. Those communities would shoulder the $420
million estimated cost.

Glade Reservoir is a sign of evolution among water managers, says Brian
Werner, a spokesman for the Northern Colorado Water Conservancy
District. The district began pursuing the project after a previous
attempt at a dam led to the Poudre's designation as Colorado's only
wild and scenic river.

Werner says that Glade is a cautious -- and necessary -- first step
that could return flows to the Poudre even as it protects local
agriculture against buyouts by booming communities and helps meet
regional water demands for the next few decades.

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We really shouldn't call this water development. It really is just water reallocation. No new water is being developed. Every time we reallocate water in substantial quantities, we do so crudely. This is probably just a little less crude than in the past but we really don't understand the impacts.

There was no mention of the siltation rates. What is the longevity of these mega-scale, industrial age solutions? 50 years? 100 years? Certainly, it will be long enough for mindless development to siphon off handsome profits before they discover they are once again threatened with water deficits. I guess it doesn't really matter, climate change, peak oil, and growing water scarcity will soon be shutting things down.